The effect of light intensity on incomplete resistance of coffee to Hemileia vastatrix

Resistance of coffee to race II ofHemileia vastatrix was tested in different environments at light intensities (LI) from 17 to 100% of total outdoor radiation. Nine treatments, in which three levels of LI before inoculation were combined with three levels of LI after inoculation, were applied to seedlings of the susceptible cv. Mundo Novo. Higher LI before inoculation induced a significant increase in lesion density, whereas the opposite was observed for treatments after inoculation. Maximum differences in lesion density were threefold. The interaction between pre-and post-inoculation treatments was also significant. Necrosis of lesions occurred under extremely high LI after inoculation.Genotypes of the Icatu population and ofCoffea canephora cv. Kouillou, which varied in disease level in the field, were tested in different environments, constant LI being applied before and after inoculation. Most genotypes were more resistant at low LI than at high LI, paralleling the results obtained for the control cv. Mundo Novo. With cv. Kouillou, sporulating lesion density, latency period and reaction type were significantly affected by LI and genotype. The interaction between LI and genotypes was significant for sporulating lesion density and reaction type, mainly because the most resistent genotype was not affected, or affected in opposite direction, by LI.Environment affected the expression of the resistance gene S_H4. Observations on a segregating F2 population indicated dominant gene action in the greenhouse (low LI) and incomplete dominant to nearly recessive gene action in the nursery (high LI). Incomplete dominance was expressed by heterogeneous to susceptible reaction types of heterozygote plants (S_H4s_H4), under high LI.Some ecological and breeding aspects of the observed effect of LI on resistance to coffee leaf rust are discussed.Samenvatting Resistentie van koffie tegen fysio II vanHemileia vastatrix werd getoetst in milieus bij lichtintensiteiten (LI), die varieerden van 17 tot 100% van de totale instraling. Negen behandelingen, bestaande uit de combinaties van drie niveaus van LI vóór inoculatie en drie ná inoculatie, werden toegepast op zaailingen van het vatbareCoffea arabica ras Mundo Novo. Toenemende LI vóór inoculatie veroorzaakte een significante toename in lesiedichtheid, terwijl het tegenovergestelde werd waargenomen bij de behandeling na inoculatie. Maximale verschillen in lesiedichtheid waren drievoudig. De interactie tussen behandelingen vóór en ná inoculatie was ook significant. Bij extreem hoge LI ná inocultie trad necrose van de lesies op.Genotypen van de Icatu populatie en van hetC. canephora ras Kouillou, met verschillende ziektescores in het veld, werden beproefd in verschillende milieus, waarbij een constante LI voor en na inoculatie werd toegepast. De resistentie van de meeste genotypen kwam beter tot uiting bij lage LI dan bij hoge LI, wat ook waargenomen werd voor het controle ras Mundo Novo. Bij het ras Kouillou werden de dichtheid van sporulerende lesies, de latentieperiode en het reactietype significant beïnvloed door LI en genotype. De interactie tussen LI en genotype was ook significant voor dichtheid van sporulerende lesies en voor reactietype, voornamelijk doordat het meest resistente genotype niet, of in de omgekeerde richting, beïnvloed werd door LI.De expressive van het resistentiegen S_h4 bleek ook afhankelijk van het milieu. Waarnemingen aan een uitsplitsende F2-populatie duidden op een dominante genwerking in de kas (lage LI) en een incompleet dominante, of bijna recessieve, genewerking in de kwekerij (hoge LI). Deze incomplete dominantie uitte zich d.m.v. heterogene tot vatbare reactietypes van heterozygote planten (S_H4s_H4) onder hoge LI.Enkele ecologische en veredelingstechnische aspecten van de waargenomen invloed van LI worden besproken.     

The use of leaf disk inoculations in assessing resistance to coffee leaf rust (Hemileia vastatrix)

The suitability of inoculations of leaf disks of 1.8 cm diameter in determining resistance of coffee toHemileia vastatrix, the causal agent of coffee leaf rust, was studied. Results obtained by this method were similar to those obtained by greenhouse tests with respect to reaction types of coffee plants with complete and/or major gene resistance. The efficacy of the method in assessing incomplete resistance was tested on 19 plants ofCoffea canephora cv. Kouillou, which varied in level of disease in the field. Four series of inoculation were carried out in four different months of the year, and six components of resistance were assessed. The analysis of multiple correlation, applied to the average data of the four series, indicated that 79% of the variation in disease in the field could be explained by the observations in the leaf disk test. For the individual series this percentage varied from 58 to 70. The coefficients of correlation between the six components were significant and high. The percentage of leaf disks with sporulating lesions was found to be the most suitable component for assessing incomplete resistance.The number of lesions per leaf disk was affected substantially by the hour of the day of leaf collection and by light intensity in the field. No effect was observed of the size of the disks (1 to 2 cm in diameter) and of the leaf wetness period after inoculation (24 and 48h). Results were more consistent when the inoculum was applied in droplets of 0.025 ml than when the inoculum was sprayed onto the disks. No genotype x treatment interactions were observed for the hour of leaf collection, for the size of the leaf disk, for the inoculation method or for the leaf wetness period.It is concluded that the leaf disk method, if adequately standardized, can be a very useful tool in breeding for coffee leaf rust resistance and also in basic research on the coffee —H. vastatrix relationship.Samenvatting De geschiktheid van inoculaties van bladschijven van 1.8 cm diameter voor de bepaling van resistantie van koffie tegenHemileia vastatrix, de veroorzaker van koffieroest, werd nagegaan. Voor het bepalen van het reactietype van koffieplanten, met complete en/of monogene resistentie, bleek de bladschijfmethode resultaten op te leveren die vergelijkbaar waren met die van kasproeven. De geschiktheid van de methode voor het bepalen van onvolledige resistentie werd beproefd bij 19 planten, behorende tot het ras Kouillou vanCoffea canephora, die varieerden in veldaantasting. Vier inoculatie series werden uitgevoerd in vier verschillende maanden van het jaar, waarbij zes resistentie-componenten werden bepaald. Multipele correlatie voor de gemiddelden van de vier series toonde aan dat 79% van de variatie in veldaantasting te verklaren was door de waargenomen componenten in de bladschijftoets. Voor de individuele series varieerde dit percentage tussen de 58 en 70. De zes componenten vertoonden onderling een sterke mate van correlatie. Het percentage bladschijven met sporulatie bleek de meest geschikte component te zijn voor het schatten van onvolledige resistentie.Het aantal lesies per bladschijf werd duidelijk beïnvloed door het uur van de dag waarop de bladeren werden geplukt en de hoeveelheid licht waaraan de bladeren waren blootgesteld in het veld. De grootte van de bladschijven (1 à 2 cm in diameter) en de bladnatperiode na inoculatie (24 en 48 uur) bleken hierop geen effect te hebben. De inoculatiemethode, waarbij druppels van 0,025 ml werden gebruikt, bleek meer consistente resultaten te geven dan de methode waarbij het inoculum op de bladschijven werd gespoten. Er werd geen genotype x behandeling interactie waargenomen voor het uur van de dag waarop de bladeren werden geplukt, de grootte van de bladschijven, in inoculatiemethode en de duur van de bladnatperiode.Geconcludeerd wordt dat de bladschijfmethode, mits toegepast in gestandaardiseerde vorm, een zeer bruikbaar hulpmiddel kan zijn bij de veredeling van koffie op roestresistantie en bij het onderzoek naar de relatie tussen koffie enH. vastatrix.     

Genetic diversity and structure of Hemileia vastatrix populations on Coffea spp.

Coffee leaf rust is the most limiting disease for coffee cultivation in Brazil. Despite its importance, relatively little is known about the genetic diversity of Hemileia vastatrix, the rust causal agent. In this work, the DNA from 112 monopustule isolates from different geographic locations and coffee genotypes were analysed by amplified fragment length polymorphisms (AFLP). The objectives were to assess the influence of the host and geographic origin on the diversity and population differentiation in H. vastatrix. The fungal population showed a low level of genotypic diversity. Gene diversity (h) was 0·027 and the hypothesis of random mating in the total population was rejected, but evidence for recombination was found for two subpopulations (São Paulo and Paraná). The analysis of molecular variance revealed that 90% of the genetic distribution of the pathogen occurs among isolates within the subpopulation (states or host of origin). There was no correlation between geographic and genetic distance (r = ?0·024, P = 0·74), which together with the high number of migrants and the low degree of differentiation in populations of H. vastatrix, is consistent with the fact that the inoculum is probably easily dispersed by wind over long distances, allowing dispersal of the pathogen among coffee growing areas in Brazil. Therefore, it is difficult to predict the durability of resistant sources to coffee rust. The recommendation for the breeding programmes is thus to incorporate multigenic resistance as a control strategy.     

Temperature requirements for germination,germ tube growth and appressorium formation of urediospores of Hemileia vastatrix

Requirements for germination, germ tube growth and appressorium formation of urediospores ofHemileia vastatrix, the causal organism of coffee leaf rust, were investigated by applying treatments with constant temperatures, ranging from 10 to 31°C, and with variable temperatures. Observations were made after 4, 6, 8 and 24 h of incubation of the spores in distilled water on glass slides. The lower and upper limits for germination were estimated to be 13 and about 30°C, respectively. Germination was quickest at 22 to 28°C, whereas appressoria formed more rapidly at 13 to 16°C. After 24 h of incubation, a broad optimum, from 16 to 28°C, was observed for germinationn and total appressorium formation. The shape of the appressoria was torpedo-like or roundish at 13 to 19°C, whereas at higher temperatures their shape was predominantly irregular. Germ tube length increased linearly with time, with an optimum at 19 to 22°C. The degree of branching of the germ tube was positively correlated with germ tube length. Germination percentage and appressorium formation were higher on leaf disks than on glass slides. With variable temperatures, significant correlation were found between temperature sum and percentage of germination, appressorium formation and germ tube length.The results show that germination and appressorium formation can occur at lower temperatures than reported in literature. Penetration byH. vastatrix seems te be realized most rapidly in nature, if, after wetting of the spores, a decline in temperature occurs from initially ca. 23 to 17°C within a few hours. Such conditions prevail during evening and early night in many areas where Arabica coffee is grown.Samenvatting De temperatuurbehoeften voor kieming en appressoriumvorming van uredosporen vanHemileia vastatrix werden onderzocht door incubatie bij constante temperaturen, 10 tot 31°C, en variabele temperaturen. Waarnemingen werden gedaan na 4, 6, 8 en 24 uur incubatie van de sporen in gedestilleerd water op glasplaatjes. De onder- en bovengrens voor kieming bleek bij 13 en ca 30°C te liggen. De kieming kwam het snelst op gang bij 22 tot 28°C en de appressoriumvorming bij 13 tot 16°C. Na 24 uur incubatie werd een breed optimum waargenomen van 16 tot 28°C voor het kiempercentage en het totale aantal appressoria. De vorm van de appressoria was torpedoachtig of rond bij 13 tot 19°C, terwijl bij hogere temperaturen de vorm meestal onregelmatig was. De lengte van de kiembuis nam vrijwel rechtlijnig toe met de tijd, met een optimum van 19 tot 22°C. De vertakkingsgraad van de kiembuizen was positief gecorreleerd met de kiembuislengte.Kieming en appressoriumvorming verliepen beter op de bladschijven dan op glasplaatjes. Bij de behandelingen met variabele temperaturen werden significante correlaties waargenomen tussen de temperatuursom en de kiembuislengte en ook tussen de temperatuursom en het kiem- en appressoriumpercentage.De resultaten tonen aan dat kieming en vooral appressoriumvorming bij lagere temperaturen kan plaatsvinden dan verondersteld in de literatuur. Ze suggereren dat penetratie vanH. vastatrix het snelst gerealiseerd kan worden in de natuur als, na bevochtiging van de sporen, een temperatuurdaling plaatsvindt van aanvankeljk ca. 23 naar ca. 17°C binnen een paar uur. Deze conditie komt veelvuldig voor in de namiddag en het begin van de nacht in vele gebieden waar Arabica-koffie wordt verbouwd.     

The effect of leaf age on infection of Coffea genotypes by Hemileia vastatrix

The age of a leaf at the time of inoculation affected both development of infection structures on the leaf surface and subsequent sporulation. In the case of the susceptible genotypes, cv. Caturra and line NC-169, there was a decrease in the number of appressoria formed, with an increase in age of fully expanded leaves. On the selected resistant line, NP-547, significantly fewer appressoria were formed on the fourth leaf pair than on younger or older leaf pairs. Appressoria were formed significantly more readily over stomata of leaf pairs one, two, three, four and six than over five and seven of the susceptible selections. On the youngest leaf pair a significantly large percentage of appressoria formed away from stomata compared with the percentages obtained for older leaf pairs, where a large proportion of germinated uredospores did not form appressoria. The reaction type of the susceptible genotypes was a greater value on younger than older leaf pairs, and the reverse was true of the resistant genotype. The latent period (inoculation to sporulation) was shorter on NC-169 than on cv. Caturra. No uredospores formed on NP-547. Uredosorus density decreased with an increase in leaf age on the susceptible genotypes.     

小麦持久抗条锈病品种Champlein的抗性遗传分析

小麦条锈病是小麦生产中最重要的病害,培育抗病品种是防治条锈病最经济、有效、安全的措施。‘Cham-plein’引自法国,对条锈菌生理小种表现良好持久抗性。为了明确其抗性遗传特点,以感病品种‘铭贤169’与其杂交、自交和回交获得了F1、F2、F3和BC1代,人工接种小麦条锈菌生理小种CY32,在温室和田间对‘Champlein’进行遗传分析。结果表明:苗期‘Champlein’对CY32的抗病性由1对显性基因控制;成株期‘Champlein’对CY32的抗病性由2对显性和1对隐性抗条锈病基因以互补方式控制;系谱分析表明基因可能来源于‘Vilmorin27’。     

小麦持久抗性品种对中国条锈菌(系)抗病性特点的分析

小麦品种抗性谱鉴定、田间病情系统观察和抗性组分测定等结果表明,小麦持久抗条锈品种具显著的抗性特征,即成株期抗性谱很宽,有的品种甚至全生育期都表现抵抗,田间病情消长很慢且轻,成株期一般表现侵染机率低、病斑面积小、潜育期长。试验在控制条件下进行,便于操作,可用于小麦品种持久抗条锈性鉴定研究。     

诱导小麦抗叶锈病生防细菌的筛选、鉴定及其防效评价

小麦叶锈病是小麦生产上的重要病害,防治该病害主要采用抗病品种和喷施化学农药,而探索生物防治是防治该病的一种新方法。本研究使用3株细菌菌悬液对小麦种子进行处理,于小麦一叶期接种叶锈病菌10d后调查其发病率和严重度。结果表明,在盆栽试验中,Sneb1462菌株菌悬液诱导小麦抗叶锈病的效果最好,可使发病率和严重度比对照分别降低27.54%和49.90%;Sneb1462还可促进小麦根部生长,施用后小麦根长和地下部鲜重分别比对照提高30.19%和29.03%。在大田试验中,用Sneb1462菌悬液处理小麦种子后叶锈病的严重度降低38.60%,小麦株高和穗重分别提高16.44%和34.98%,表明该菌株是一株优良的抗病促生菌。经透射电镜观察、16SrDNA序列分析及生理生化的检测,鉴定该菌株为多黏类芽胞杆菌Paenibacillus polymyxa。利用生防细菌Sneb1462进行种子处理防控小麦叶锈病将是一种新型的植保措施,具有重要的研究意义。     

玉米灰斑病抗性鉴定技术

对玉米灰斑病菌孢子产生、病菌接种和寄主抗病性测定技术的研究结果表明，应用玉米叶粉碳酸钙琼脂和玉米叶粉琼脂两种培养基，温度24～25℃，培养5天，病菌可大量产生分生孢子；于植株喇叭口期，用注射器将病菌孢子悬浮液注射于植株喇叭口中，获得了理想的发病效果；对20个玉米自交系注射接种鉴定结果表明，玉米自交系间抗病性差异明显，但未发现免疫自交系。     

甘肃陇南小麦不同品种类型抗条锈性变化特点分析

 1973~2002年的30年间,在我国小麦条锈病常发易变区的陇南,对小麦主要生产品种的抗条锈性变化动态进行了系统的观察,选择具垂直抗性、慢条锈性、高温抗性和持久抗性等不同类型的7个品种的观测数据进行了分析,认为里勃留拉和N.斯特拉姆潘列长期保持了稳定的抗锈性。里勃留拉的抗性可能由多对微效基因控制,N.斯特拉姆潘列的抗性可能由主效基因控制,兰天12号所具有的慢锈性和兰天1号的高温抗性以及抗条锈基因的合理布局对延长品种抗性也有一定作用。     

小麦慢条锈品种成株期抗性组分分析

经2001-2003年对典型慢条锈品种成株期抗性组分测定结果表明,慢条锈品种具有如下特征:反应型和普遍率与快条锈品种差异不大,但病情指数低且上升速度缓慢;侵染点数少;潜育期相对较长;相对寄生适合度较小;对产量构成因素的影响不大等特点。提出了潜育期和病情指数是田间鉴定品种慢条锈性与否的简易、快速方法。     

向日葵品种叶片组织结构与抗锈病的关系

向日葵锈病是向日葵的重要病害之一,在世界向日葵生产地区普遍发生,给向日葵产业带来巨大的经济损失。本研究通过比较向日葵抗、感锈病品种叶片组织结构的差异,以揭示此类病菌与寄主间的相互作用及其寄主抗病机理,研究结果表明：抗病品种叶片蜡质含量高于感病品种,且栅栏组织双层,排列整齐、紧密,可以抵抗病菌的侵入和扩展,而气孔密度与抗病性没有相关性。     

二倍体及四倍体中抗叶锈病基因在双二倍体中的表达与抑制

 通过杂交将近缘植物中的抗病基因导入普通小麦是抗病育种的常用方法。在利用二倍体和四倍体杂交合成双二倍体小麦过程中, 二倍体或四倍体携带的抗叶锈病基因在双二倍体中大多数情况下可以完全表达或部分表达其固有的抗病性, 但部分抗叶锈病基因则不能表达。四倍体波斯小麦Ps5、Ps8和野生二粒小麦D s3含有相同的抗叶锈病基因LrPs (暂定名), 在双二倍体Am1、Am2、Am3、Am5和Am7中可以表达其抗病性, 但在Am4中不能表达;二倍体粗山羊草Ae37含有Lr41和未知基因, 但Lr41在双二倍体Am2中不能表达;四倍体硬粒小麦Dr147携带Lr23和未知基因, 在双二倍体Am6中不能充分表达。抑制基因的存在是导致抗病基因不能表达或部分表达的主要原因之-。抑制基因位于AB染色体组或D染色体组上, 其抑制作用对抗病基因和病菌致病类型具有专化性, 还可能受温度等环境条件和寄主遗传背景等因素的影响。遗传分析结果表明, 在常温下, 双二倍体Am1、Am2、Am3和Am5对叶锈菌致病类型DGS/HB的抗病性均由1对相同的隐性抗病基因LrPs (暂定名)控制, 与它们具有共同的四倍体亲本Ps5有关。Am4不具有苗期抗叶锈病基因, 但含有来自粗山羊草A e39的1对隐性抑制基因SuLrPs (暂定名), 可抑制Am1、Am2、Am3和Am5中隐性抗叶锈病基因的表达。对抗病抑制基因存在原因和遗传分析验证方法等进行了讨论。     

甘肃36个小麦生产品种抗叶锈病基因分析及成株期抗性评价

为明确甘肃省主要小麦品种可能含有的抗叶锈病基因状况,用来自甘肃不同地区的22个小麦叶锈菌生理小种,在苗期对测试品种进行抗叶锈基因推导,并对这些材料进行成株抗叶锈性鉴定。结果表明,在已知抗叶锈病基因中,Lr2B、Lr13、Lr16、Lr22A、Lr30和Lr14B等基因以单基因或基因组合的形式分别分布在‘灵选6号’‘会宁15’‘兰天37’‘陇鉴113’‘兰天151’‘兰天134’和‘兰天40’等7个小麦品种中。‘陇鉴111’‘兰天31’‘陇鉴9343’‘天选67’和‘天选65’等14个品种可能含有与供试已知基因不同的抗性基因,‘中梁35’‘陇鉴110’‘陇原931’和‘天选57’等15个小麦品种推导其不含有供试的抗叶锈病基因。成株期抗叶锈性鉴定表明:‘陇原931’‘陇鉴9343’‘天选57’‘天选67’‘兰天31’‘临麦22’‘兰天134’‘兰天151’‘陇鉴113’‘陇麦838’和‘中梁35’具有较好的成株期抗性,具有抗叶锈病应用潜力。     

四川省17个主栽小麦品种中Lr26和Lr19检测

正小麦叶锈病是一种重要的小麦病害,培育和种植抗病品种是最为经济有效的防治方法。我国在小麦抗病育种工作中引入了1BL/1RS易位系,已知小麦抗病基因Lr26、Pm8、Yr9和Sr31均位于1BL/1RS易位系上~([1])。然而目前Lr26已丧失抗性~([2]),所以育种过程中需要谨慎考虑Lr26的使用。Lr19来源于长穗偃麦草~([3]),在我国目前为有效的     

青稞种质资源对条纹病的抗性鉴定

条纹病是青藏高原青稞生产上的重要种传病害之一, 常采用药剂拌种防治，但培育和推广抗病品种是防控该病害最经济有效的措施。为发掘抗条纹病的优良青稞种质资源, 本研究以田间鉴定和利用2个菌株室内人工接种鉴定相结合的方法, 对231份青稞种质资源进行了抗条纹病评价, 获得免疫性遗传资源材料20份, 高抗类型材料18份, 中抗类型材料44份, 分别占鉴定总资源数的8.7%、7.8%、19.1%;其他149份青稞资源材料对条纹病表现为感病, 其中36份材料为中度感病类型, 113份材料为高度感病类型, 感病材料占总鉴定材料的64.5%。     

青海青稞主栽品种(系)对条纹病和云纹病的抗性鉴定

本研究旨在明确青海青稞主栽品种和后备品种对条纹病和云纹病的抗性,以期为抗病育种及田间病害防治提供理论依据。试验采用田间自然病圃法,对青海主栽的30个青稞品种(系)进行了条纹病和云纹病田间抗性鉴定。结果表明,供试青稞品种(系)对2种病害的抗性存在显著差异,但缺乏免疫品种。对条纹病表现高抗的有13个品种(系),占鉴定总数的43.3%,其中主栽品种有3个,即‘门农1号’、‘昆仑13号’、‘巴青1号’。品系17发病率最低。对云纹病表现高抗的有品系1、品系2、品系6、品系17、品系28、RQKQ-3、RQKQ-5、RQKQ-6、RQKQ-7、RQKQ-8、‘门农1号’、‘互青2号’、‘北青6号’和‘昆仑10号’,共14个,其病情指数均在10以下;表现中抗的共有8个,分别为品系5、品系11、RQKQ-1、RQKQ-9、‘巴青1号’、‘北青3号’、‘北青7号’和‘昆仑13号’。     

Genetic relationship between the adult plant resistance gene Lr12 and the complementary gene Lr31 for seedling resistance to leaf rust in common wheat

A resistant phenotype similar to that conferred in wheat by the complementary genes Lr27  +  Lr31 was produced in the progeny of intercrosses of cultivars carrying Lr27 and a line possessing Lr12 . This confirms that Lr12 is either completely linked with Lr31 or is the same gene. On the basis of these findings and that Lr31 is located on chromosome 4BS, it is concluded that Lr12 must also be located on 4BS. Adult-plant genetic tests confirm that the Australian wheat cultivar Timgalen carries Lr12 , and stocks with Lr12 alone were established from this cultivar.     

大麦抗条纹病基因的定位分析

为发掘大麦中抗条纹病的新基因,采用三明治法通过人工接种大麦条纹病菌Pyrenophora graminea强致病力菌株QWC对甘啤2号(免疫)与Alexis(高感)杂交F_1代及F_2代分离群体进行抗性遗传分析,利用群体分离分析法鉴定与抗病基因连锁的SSR标记,并通过QTL IciMapping软件构建遗传连锁图谱完成对抗病基因的定位。结果显示,甘啤2号与Alexis杂交F_1代对大麦条纹病菌强致病力菌株QWC表现为免疫,F_2代表现3∶1抗感分离,表明甘啤2号对菌株QWC的抗性由1个显性抗性基因控制,将该抗病基因暂命名为Rdg3;该基因位于大麦7H染色体上的SSR标记Bmag206和Bmag7之间,与二者的遗传距离分别为1.78 cM和2.86 cM。经与已定位于7H染色体上的抗病基因比较,发现Rdg3是一个新的抗条纹病基因,可作为大麦抗病育种的新种质资源。     

Identification of molecular markers linked to a gene conferring resistance to coffee berry disease (Colletotrichum kahawae) in Coffea arabica

Coffee berry disease (CBD) caused by Colletotrichum kahawae is a major constraint to Arabica coffee (Coffea arabica) production in Africa. One source of resistance to the disease is a natural interspecific hybrid between C. arabica and C. canephora and its derivatives. This study is aimed at deciphering the genetic basis of the host resistance and identification of molecular markers associated with it. CBD is a mature stage disease and in the absence of a mature mapping population, early detection of disease reaction phenotypes of mapping individuals is required. Two F₂ populations from crosses of cv. Catimor (resistant) and cv. SL28 (susceptible) were screened for resistance by a two step procedure. First, half of each population was screened 6 weeks after germination by inoculating hypocotyls with the pathogen. The surviving seedlings (G1) were considered to be resistant and were raised in a nursery together with the other unscreened halves (G2). Secondly, after one year, all the seedlings (G1 + G2) were screened by inoculation. Analysis of 57 microsatellites and 31 AFLP markers in 56 and 95 seedlings from G1 and G2, respectively, were performed. Eight AFLP and two microsatellites markers linked tightly to the resistant phenotype were identified and mapped to one unique chromosomal fragment introgressed from C. canephora. The gene conferring the resistance was localized within an 11 cM segment. It is concluded that the locus carries a major resistance gene designated Ck‐1, which is likely to be synonymous to the T gene described in previous studies.